We propose to test the hypothesis that the implementation of treatment based upon results of clinical trials in retinopathy of prematurity, diabetic retinopathy, and glaucoma benefit not only the patient, but result in net societal savings as well. In order to achieve this objective we will: 1. Develop a computer-based program (PROPHET) that simulates the natural history of potentially binding ophthalmologic disease and models the medical and economic benefit of screening and treatment approaches for their control. 2. Use this model to project the medical and economic effects of specific forms of treatment that have been shown in clinical trials to modify the natural history of diabetic retinopathy, retinopathy of prematurity, and glaucoma. 3. MOdel the medical benefits in terms of person-years of vision saved associated with alternative screening and treatment programs that might be implemented at the population level. We will simultaneously study the net cost or savings associated with those programs from the perspective of federal, state, and local institutions. The actual impact of new treatments in the population depend heavily on the rate of patient participation. We will analyze data on the bases or varying rates of participation and model the medical and economic benefits associated with programs designed to increases participation. 4. Assess the economic return to the federal government on the investment in multicenter clinical trials that were needed to prove the efficacy of those treatments. In this way we aim to study the cost or savings associated with developing new technology. 5. Once the modeling program has been refined and its projections validated, we plan to train investigators in other regional centers who may wish to apply this technique to their areas of interest. We will achieve this aim by making the PROPHET modeling system available to other investigators and by offering workshops on its use. Data on the natural history of disease and effect of treatment will be drawn from cross-sectional studies and multicenter clinical trials. Medicare data provide charges for these procedures, as well as the frequency with which they are performed. Social Security Administration reports provide information on governmental costs of blindness related disability. The PROPHET modeling system will be used to project the person-years of sight saved under alternative screening and treatment strategies. Cost-effectiveness will be reported in terms of dollars spent per year of sight saved. Cost-benefit analysis will predict net governmental savings. These net savings will be used to calculate the return on investment generated by the clinical trials involved. The analytic strategies to be refined under this grant will be broadly applicable to other chronic and potentially blinding eye diseases.